Primal Speedbike Fairing Construction Using Precision Board

Coastal Enterprises, manufacturers of Precision Board HDU, is proud to host guest blogs written by some of the industry’s biggest movers and shakers, posted to the Precision Board Blog. This guest blog is written by George Leone, a long-time member of the Human Powered Vehicle (HPV) racing scene, and Team Captain for Team Primal. In this guest blog (part 1 of 3), George elaborates on the team’s progress towards fabricating Primal 3 using Precision Board and competing at the Human Powered Vehicle Speed Challenge near Battle Mountain, Nevada in September 2021 (this year’s event was cancelled).

Tom Robinson who helped me drive the truck and trailer, Matt Beccue does CNC work for Safran Aerospace & coordinated the project there, and Judy Lantaca, one of my favorite former Student Technicians at Cal Poly San Luis Obispo.

In George Leone’s own words…

After almost 5 years of chassis design and construction, precise aerodynamic design and computer simulation, we are poised to create the fairing for Primal 3, a streamlined, enclosed bicycle using 15 lb./cu./ft. Precision Board in the manufacturing process. This muscle-powered vehicle is designed for extreme speeds, far faster than you can legally drive on the freeway. A previous blog years ago featured Primal 2 which exceeded 70 mph three times using muscle power alone, on the flat road at the World Human Powered Speed Challenge held annually near Battle Mountain, Nevada.

We chose Precision Board not only for it’s great workability and consistency, but also for it’s high recyclables content. Our speedbike (also known as a Human-Powered Vehicle or HPV) is not only raced for records, but acts as a demonstration of what the future of transportation holds for us. Lightweight, extremely aerodynamic, structurally safe vehicles that use a minimum of effort to achieve energy efficiency. The recyclables content of the Precision Board used in its manufacture fits our futuristic agenda perfectly.

Pickup and transport to Safran Aerospace for CNC work.

We picked up two custom bonded blocks of foam for the right and left sides of the fairing in early March 2020. It was great seeing the clean, state of the art manufacturing facility that Coastal Enterprises runs. I used to run the Student Projects Shop at Cal Poly San Luis Obispo and always look at shops with a critical eye for cleanliness and safety.

The custom bonded blocks the we received had bond lines that were flawless, and the PB Bond 240 used as an adhesive that guaranteed there would be no “chunking out” of a hard adhesive, damaging the foam during the machining process. I’ve bonded a lot of foam in the last 40+ years and I was very impressed with the quality of the bond lines. From now on, I will definitely have Coastal Enterprises make custom bonded blocks for me. Not only does this save “gluing” time, it also saves re-work time to repair chunks of hard adhesive torn out by the CNC router or by the hand tools that I use.

My neighbor Jim McEntire, who restores tractors and vintage Ford cars, graciously loaned his pickup truck and a heavy duty trailer to bring the foam blocks to Safran Aerospace in Santa Maria, CA and from there home to my barn 4 hours North of Los Angeles, near Atascadero, CA.

We left Orange, California, the home of Coastal Enterprises, at almost rush hour and had to drive through Los Angeles. Somewhere in traffic in LA, I received a text from my friend and Cal Poly SLO Shop Manager, Eric Pulse, who I worked with for years. “So I see you’ve got the foam and are driving it North” !!! I replied “What the heck, how could you know this?” (I had not mentioned to anyone that I was getting the foam at that time.) Eric came back “Oh, a former student saw a truck towing a trailer with foam on it, and figured it was you. He thinks he saw you as a passenger.” (My old friend Tom Robinson was driving at the time). I swear, I could never rob a bank, someone would recognize me right away!

We delivered the Precision Board HDU three hours later to Safran Aerospace in Santa Maria, CA, as they had generously offered to CNC machine the aerodynamic body shape into the foam. Matt Beccue, the CNC supervisor, met us and we offloaded the foam and then drove the truck and empty trailer home.

The blue “Dychem” lines on the foam were done to verify the location of the surface as the project progressed.

Stay tuned for Part 2 and Part 3!

George Leone has a long history with Cal Poly San Luis Obispo and is a fount of knowledge when it comes to both composites and Human Powered Vehicle Racing. He volunteered sporadically helping Cal Poly’s HPV teams from 1980 to 1989, and then continuously from 1989 to the present. George also ran the Cal Poly Projects Shop from 2001 to 2017. This shop includes facilities for machining, student welding, woodworking, sheet metal work, advanced composites and design space for senior projects, as well as nine engineering clubs that compete at a national level. He has also built and raced his own HPVs since 1988.

ABOUT TEAM PRIMAL

Team Primal consists of a group of friends, current Cal Poly Professors and former students. It is privately funded and is not sponsored by Cal Poly in any way.

ABOUT COASTAL ENTERPRISES

At Coastal Enterprises, we like to look at the composites industry as a fully collaborative effort. Every fresh new development by an individual is really a contribution to a collective knowledge base. Like any scientific pursuit, the most potent advancements are made when information is shared freely between likeminded groups of people. For this reason, we feel obliged to do everything we can to enlighten and empower the future community of composites professionals. That’s why we support school programs with donations of Precision Board HDU. Click HERE to find out more about the program or give us a call with your questions at 800-845-0745.

Cal Poly Human Powered Vehicle Breaks 26 Year Old School Record!

Last year we brought you the story of how engineering students at Cal Poly used Precision Board urethane tooling to make fairings for their human-powered vehicle. We also told you that the team withdrew from the ASME competition and decided instead to compete at Battle Mountain, Nevada in September 2019 in order to beat the U.S. collegiate team speed record of 61.3 miles per hour. Hit the link below to see how they did and read the harrowing story of the competition, including video of a crash that ended up being a real test of the team’s built in safety measures.

From George Leone:

The Cal Poly San Luis Obispo HPV Team completed their fully enclosed Human Powered Vehicle “Ambition” just five days before competition. In the process they had to abandon a glitchy video vision system in favor of installing last-minute windows!

The event was the World Human Powered Vehicle Speed Competition (WHPSC) near Battle Mountain, Nevada in September 2019. On the second day of racing Josh Gieschen, the student pilot/motor, attained 64 miles per hour, exceeding UC Berkeley’s 26 year-old US collegiate record of 61.29 mph. But the wind was over the 3.7 meters per second limit, too strong to be “legal”, so no record was allowed.

This became a pattern for the rest of the week, with their speeds going as high as 66 mph twice, frustrating the team again and again with “illegal” winds. Leading up to the last day, Cal Poly only had one “legal” wind run, which was 1/10th mile an hour slower than the record.

It came down to the last day, Saturday. They were ceded in the second heat of the morning. Josh got into the bike, the team taped the seams of the shell closed, launched and followed in the school van. He did 63.11 mph, but was frustrated because the wind was “illegal” once again. That looked like the end of it for the year.

The Team drove back to start and requested to run again in the fourth and last heat. It’s rare to attempt two runs so close together because the “motor” usually can’t recover that quick, but Josh was adamant.

Veteran racer Peter Borenstadt graciously gave up his position in that heat so that Cal Poly could have another chance. That’s how HPV Racers are.

Cal Poly became serious, quietly taping the pilot in and launching. Josh gave it everything he had left. Just before the bike reached the crew in the “catch zone” (riders are fully enclosed and can’t put their feet down) an exhausted Josh grabbed the brakes too hard. The rear tire blew.

Ambition suddenly pitched sideways and pencil-rolled four times, amazingly ending upright beside the road to be caught by the crew. Because all the safety and restraint systems worked perfectly Josh exited with only a few bruises, and only a few scratches on the body of the bike.

Then they waited for the timer’s report on the radio. “Ambition: 63.68 miles per hour; wind is legal. Congratulations Cal Poly – you have a record!” The team went crazy!

Read more about their record breaking run HERE and also catch up on our original blog where the team used Precision Board urethane tooling to fabricate their HPV.

How Berkeley Formula Racing Uses Precision Board Tooling

The following Precision Board Guest Blog is written by Hunter Wheeler, a student of engineering at U.C. Berkeley. Hunter is part of the Berkeley Formula Racing program and describes how the Formula SAE Team used Precision Board urethane tooling board to make one-off molds for the carbon fiber pieces of their race car.

In Hunter’s own words…

The Precision Board tooling board donations provided to us by Coastal Enterprises is an invaluable part of our manufacturing and we wouldn’t be able to make our carbon fiber aerodynamic package, bodywork, or custom seat without it (Ed note: Coastal provides material to schools through our Donation Program. Students will typically bond pieces together for their final product). I’ll give a brief rundown of our design and manufacturing process in this blog.

We begin our design season by learning and reviewing aerodynamics fundamentals from textbooks and research papers. We set specifications for our target CLA (Downforce), CDA (Drag), package weight, and center of pressure using a LapSimulation model written by members of our team in MATLab. This model simulates the race car driving the different events at competition and gives an estimated points gain (or loss) for changes in parameters such as those listed above. We choose designs to pursue for the season after an analysis of this model, testing from previous years, and through consulting literature.

We model our wings and bodywork in SolidWorks and run Computational Fluid Dynamic (CFD) simulations in ANSYS Fluent.

After design, each carbon fiber component is manufactured on a one-off urethane mold made out of Precision Board. We start by cutting the foam to the required size, and glue sheets of urethane together to reach the necessary thickness for each mold.

The foam is then machined on our customer built CNC router.

We take the 3D models of our wings from SolidWorks and convert these to coordinates the CNC router can interpret. This process gives us a female profile for each wing half. We then apply a few layers of gelcoat to the surface of the mold using a paint spray gun to achieve a hard surface that can be polished to a smooth finish.

After sanding, waxing, and buffing the gelcoat, we lay-up carbon fiber on the mold.

This is enclosed in a vacuum bag and placed in an industrial oven to cure.

After about 6 hours, the carbon fiber has cured and we are able to remove a wing half.

This process is completed for each of the wings, body work panels, and any other carbon fiber components we manufacture. We then bond these wing-halves together and do some post processing to achieve our final manufactured profiles.

You can check out a video below we made from testing our vehicle at Crow’s Landing.

The Berkeley Formula Racing team has already competed for 2019. See the results in the chart below and keep an eye out for our 2020 car!

Formula SAE is an international engineering design competition that provides ambitious college students the unique opportunity to enhance their engineering design and project management skills through practical application. Berkeley Formula Racing creates a formula-style, single-seat race car over the course of a school year in order to participate in FSAE Lincoln, a competition between 80 teams every June. The competition is comprised of dynamic events to test the vehicle’s performance and reliability, and static events, to test the rigor and feasibility of the engineering design and business strategy. The competition pushes the boundaries of conventional learning, pushing students to develop skills applicable to the professional world that are overlooked in traditional school curriculum.

Coastal Enterprises manufactures Precision Board, a versatile, cost-effective and eco-friendly urethane material used extensively in the tooling industry. It is a closed-cell, rigid, dimensionally-stable substrate that is ideal for use in a number of different tooling applications.

Request free samples, get a quote or sign up for weekly e-blasts packed with helpful information.

How Chip Load Factors into CNC Router Speeds and Feeds

We often get asked about optimal speeds and feeds settings for CNC routing of Precision Board HDU. While there is a lot of great information on our website about feeds and speeds, what doesn’t get talked about as much is something called “chip load”. Chip load can be defined as the size or thickness of the chip that is removed with each flute per revolution. There are many factors that go into calculating chip load, so we’ve put together this blog with information from router bit manufacturer LMT Onsrud and CNC manufacturer AXYZ Automation Group. Using the information in this blog, and with a little experimentation, you will be able to dial your settings in to achieve greater CNC efficiency when routing HDU. Clean, sharp edges, a smooth cutting surface and potentially shortened cutting time are all benefits of optimized CNC router settings.

LMT Onsrud

LMT Onsrud is a premium cutting tool manufacturer servicing the metal working, composite, wood and plastics (HDU) industries. Their tooling can be found within various industrial markets – aerospace, medical, composites, plastics, woods – and are used in making the products you use on a daily basis.

The proper cutting tool used with speeds and feeds information lets you achieve optimum chip load. Proper chip load allows the cutting tool to move in and out of the material quicker, leading to more efficient CNC machining.

You can optimize your chip load by setting the feed rate and cutter speed to yield the largest chip that produces the desired surface finish. Precision Board HDU is non-abrasive, which also prolongs tool life.

Here’s a useful formula:

Chip Load = Feed rate/ RPM x # of flutes

To increase chip load:

Increase feed rate
Decrease RPM
Use a cutter with fewer flutes

To decrease chip load:

Decrease feed rate
Increase RPM
Use a cutter with more flutes

Check out this video from Onsrud where they explain in more detail how to calculate speeds and feeds.

They reference a chart in the video with formulas to calculate chip load as well as speeds and feeds. You can view a version of that below.

AXYZ Automation Group

AXYZ Automation Group is a leading global manufacturer of CNC router systems and CNC knife systems. Designed and built at their state-of-the-art factory in Canada, AXYZ CNC routers are supplied and supported through a global network of sales and support offices and authorized dealers. With more than 366,918 standard machine configurations, AXYZ specializes in matching machinery to customer’s unique needs and budgets.

They have an excellent website with valuable information on CNC routing. You can find that resource HERE.

The following information is from an article of theirs on feeds and speeds and chip load.

Calculating Feeds and Speeds

There are certain parameters that must be considered, before setting up any file for cutting if you are to accomplish the finish and accuracy required. One of the most important of these factors is the Chip load per Tooth (Cpt). Chip load can be defined as the size or thickness of the chip that is removed with each flute per revolution.

When material is machined the cutter must revolve at a specific RPM and feed at a specific feedrate to achieve the proper Chip load. There are also several factors to be considered when choosing the proper RPM and feedrate.

The feed rate used depends upon a variety of factors, including power and rigidity of the machine, rigidity of part hold-down, spindle horsepower, depth and width of cut, sharpness of cutting tool, design and type of cutter, and the material being cut.

To obtain the optimum Chip load, we must consider the variables listed above, along with the machine and materials we intend to cut. This will help us find the best feed rate and RPM for any given tool and material.

One thing to remember is to make chips not dust. Chips will help by removing the heat produced in the cutting process thus increasing tool life and improving edge quality.

Feed rate is calculated using the following equation:

Feed = N x cpt x RPM

N – number of cutting edges (flutes)
cpt – chip load (chip per tooth) is the amount of material, which should be removed by each tooth of the cutter as it rotates and advances into the work. (mm per tooth)
RPM – the speed at which the cutter revolves in the spindle. (Revolutions per minute)

We will now break down the relationship between the Feed rates, number of cutting edges, chip load and RPM. For most materials there is a recommended chip load.

If you are running at 18000 RPM using a 25mm endmill with two flutes, and a recommended chip load of 0.1 mm/tooth:

Feed = 2 x 0.1 x 18000 = 3600 mm per min

If the RPM were increased to 24000 RPM the new feed rate would work out to be:
Feed = 2 x 0.1 x 24000 = 4800 mm per min

chip load

Based on this mathematical equation, as RPM increases, feed rate will also increase if all other settings remain the same. If the number of cutting edges changes, however the feed rate will either increase or decrease depending on the whether the number goes up or down. The same applies to chip load if the recommended chip load is 0.1 mm/tooth the RPM, feed or number of cutting edges may go up or down to maintain the required chip load. Therefore if chip load remains the same, and feed rate increases, either the RPM and or number of cutting edges must increase to maintain the recommended chip load.

When calculating the feed rate for any material the chip load is therefore one of the most important factors to be taken into account because the chip load determines the amount of material that each tooth will remove, plus the load that each tooth will have to take. Another factor that affects chip load is the diameter of the cutter. A larger cutter will be able to handle a larger chip load.

No of teeth	cpt (mm)	Feed rate (mm per min) at RPM
No of teeth	cpt (mm)	18000	21000	24000
1	0.1	1800	2100	2400
2	0.1	3600	4200	4800
3	0.1	5400	6300	7200
1	0.4	7200	8400	9600
2	0.4	14400	16800	19200
3	0.4	21600	25200	28800

Therefore depending on the diameter of the tool, if the RPM and number of cutter edges stay the same chip load will increase with a larger diameter cutter, thus the feed rate will also increase. When machining softer materials or using a stubby router bit the chip load can be increased. If an extra long router bit is being used, the chip load should be decreased.

For most material that you will be cutting on an AXYZ router table you will typically set the RPM between 18000 and 24000, and adjust your feed rate to obtain the required results. On an AXYZ router table we use spindles that produce a maximum of 24000 RPM. The speeds and feeds chosen can be affected by the horsepower of the spindle being used (horsepower varies from 3Hp to 10 Hp). At higher horsepower you will produce more torque thus allowing the machine to run at a variety of RPM’s (torque drops off as the RPM is reduced). For most application we typically work in the 18000 to 22000 RPM range.

Typical Chip Load Values for Various Size Cutters
Tool Diameter	Hard Woods	Softwood / Plywood	MDF / Particle Board	Soft Plastics	Hard Plastics	Aluminium
3mm	0.08 – 0.13	0.1 – 0.15	0.1 – 0.18	0.1 – 0.15	0.15 – 0.2	0.05 – 0.1
6mm	0.23 – 0.28	0.28 – 0.33	0.33 – 0.41	0.2 – 0.3	0.25 – 0.3	0.08 – 0.15
10mm	0.38 – 0.46	0.43 – 0.51	0.51 – 0.58	0.2 – 0.3	0.25 – 0.3	0.1 – 0.2
12mm and over	0.48 – 0.53	0.53 – 0.58	0.64 0.69	0.25 – 0.36	0.3 – 0.41	0.2 – 0.25

Even though there are formulas for calculating feed rates you will find that optimum feed rate will be determined from experience. You will typically start off with the calculated feed rate. Under ideal conditions it is usually suggested that the actual feed rate be set to approximately one-half the calculated amount and gradually increased to the capacity of the machine and the finish desired.

Once you have determined what feed and speed to start with, there are other factors to be taken into consideration. The next thing to be considered is the direction of cut, which is the direction the cutter is fed into the material. Conventional milling or cutting forward is the most commonly used method. With this method the work is fed against the rotation direction of the cutter. The other method is climb milling or cutting reverse. For this machining method the workpiece and the machine must be rigid. The AXYZ router machine is such a machine. When machining non-ferrous materials, climb cutting should be used to achieve a good finish.

Another factor is depth of cut. Depth of cut will effect edge finish as well as tool life. You will have to adjust your depth to achieve the desired results depending on the type of material and size of cutter. Usually a depth of cut that equals the radius of the cutter is a good starting point when cutting non-ferrous metals.

Conclusion

By experimenting with these different speeds and feeds settings, and using the chip load formula that works best for you, it’s possible to maximize your CNC efficiency. Always remember to make chips and not dust. This can potentially speed up your cutting time and help you to achieve clean, sharp edges and a smooth routing surface on your HDU. Trying a variety of cutting tools and settings will also add life to your CNC machine and save wear and tear on your cutters. When in doubt, consult the manufacturer of your CNC for best practices on chip load for your particular CNC machine.

About Coastal Enterprises

Coastal Enterprises manufactures Precision Board HDU, a versatile, cost-effective and eco-friendly urethane material used extensively in the tooling industry. It is a closed-cell rigid substrate that does not rot, warp or crack. You can request free samples, get a quote or sign up for periodic newsletters packed with helpful information.

Ten Tips for Tooling with Precision Board

With its roots in Aerospace, Precision Board Tooling Board is specifically engineered to meet the demands of a broad range of tooling and tool making applications. Both PBLT Tooling Board (for low temperature applications up to 200 F) and PBHT Tooling Board (for high temperature applications up to 300 F), possess excellent machining characteristics and dimensional stability for tool making. To help maximize your use of Precision Board, here are ten tips for tooling.

1. Using the correct speed and feed settings for the density of Precision Board you will be machining is crucial. This will allow you to achieve optimum chip load. Having the proper chip load allows the cutting tool to move in and out of the material quicker, which will prolong the tool life and leave a smooth edge. Read our updated speeds and feeds blog for the latest information. Be sure to also check out the excellent database LMT Onsrud has for choosing the right bit for the right material.

2. If using Precision Board in an oven or autoclave, ensure that temperature ramp up does not exceed 1˚F per minute. This will allow the temperature to be evenly absorbed during heat expansion, which will reduce the possibility of internal stress and warping.

3. When ramping down the temperature after autoclave or oven curing, temperature ramp down should not exceed 2˚F per minute. This will allow the tool temperature to drop slowly so contraction does not cause internal stress and cracking in the thinner sections of the tool. In thick tools with thin webs or sections, cool down should be even slower. Prior testing is always recommended before heat cycling on actual tool.

4. Instead of laminating thinner sheets together to form a large block, consider using a custom block. By providing a drawing to Coastal Enterprises, a custom-sized block will be made in the rough shape and size of your tool. This will allow you to purchase less material, eliminate assembly and reduce machining time. You can get more details in our recent custom bonded blocks blog post.

5. Precision Board does not outgas. When a typical polyurethane tooling board is heated, it outgases, which releases byproducts that keep the composite laminate adhesive from curing. This will ruin the composite laminate and can damage the urethane tool.

6. For higher temperature applications, Coastal Enterprises offers Precision Board High Temp PBHT. PBHT is a “closed cell” rigid polyurethane tooling board made specifically for applications of up to 300˚F continuous exposure. PBHT is available in a wide range of sheet sizes up to 5′ x 10′ (and thicknesses up to 24″) and several densities. It can be cut or bonded into a variety of shapes for final machining or shaping.

7. Make a master tool with Precision Board for Production Tools. For production runs it is better to use the Precision Board tool as a “master tool” to reproduce “production” tooling. This method allows for multiple production tools to be made from one Precision Board master. This is a very effective way to make lower cost, faster completion, production tooling.

8. Use high strength EP-76 Epoxy to bond Precision Board sheets to make larger sections. Precision Board can be easily bonded with high quality epoxy adhesives. Coastal Enterprises makes a very easy to use, machinable grade, high-strength epoxy called EP-76. It machines, sands and carves very smoothly. The durometer hardness and machinability of EP-76 can be adjusted and closely matched to the Precision Board densities by adding PB Granules as outlined in the PB EP-76 HDU Adhesive Product Data Sheet. Contact Coastal Enterprises for more information and helpful bonding tips.

9. Use a mold release that is compatible with your resin system to ensure neither the mold or the tool are damaged. Mold releases are designed to be used against all tooling surfaces so that after cure cycle, the composite part can be released and removed from the layup tool without damaging the tool or the part. Care must be taken when choosing a release agent to be sure it will not outgas during the composite heat curing cycle and affect resin cure. Always test a sample part to verify mold release compatibility with your chosen prepreg or composite laminate.

10. Hold down (or “dog”) Precision Board to the vacuum table or oven support fixture during heating & cooling. Due to the internal stresses that are occurring in the tool during the heating and cooling part of the cure cycle it is important to hold the Precision Board tool flat. However, due to the differential of expansion and contraction between the Precision Board lay up tool and the support structure it is crucial that they be allowed to move independent of each other. It is always a good idea to securely, not excessively, hold PBLT and PBHT tooling to the machining table to support the piece during ramp up and ramp down. Dogs, or equivalent, every 2′ +/- is adequate. Remember not to over tighten which will restrict horizontal expansion and contraction and possibly damage tool and composite laminate.

Our PBLT and PBHT lines of Precision Board are available in the widest range of densities and sheet sizes & thickness to match the performance requirements of the specific tool you’re building. Individual blocks can be easily and permanently bonded to create specific shapes and thicknesses, approximating the general shape of the tool. Coastal Enterprises offers a full line of companion products specifically designed for Precision Board Tooling Board to assist with your project. Check out our Adhesives and Primers & Fillers. Request a sample today!